It's amazing how our bodies can fool us. My left knee was fine for 17 yrs until March of 2018. One day a piece of articular cartilage broke loose from atop my tibia. It happened at the 3 minute point on an elliptical at light resistance and the resulting hole was the size of a half dollar (surgery was just weeks later). It was sticking in the joint, so we had to do surgery.
Imagine my surprise when I woke up from microfracture surgery to learn the extent of OA in that knee. It might last another 2 yrs if I'm lucky, as it's <this close> to bone on bone in all compartments. I didn't think it was that bad because my right knee was 10X worse.
My TKR surgeon did his own xrays 3 months after that surgery and said he'd actually recommend replacing it within 1-2 yrs unless I want to create more problems. I waited YEARS too long on the right knee and refuse to do so with the other.